Segment Overview
A Segment groups contacts by shared criteria so content, campaigns, or personalization can target a specific audience instead of everyone.
Once you've added a Segment, it appears in this list. Click its name to open this Overview and manage it.

Importing from a Connected Provider
If your organization has a Customer.io connection configured under Providers, a Segment can be populated from that connection instead of managed by hand. This requires a provider connection to already be set up — see your administrator if Providers isn't configured for your deployment.